Little is known about this species as it is rarely seen in the wild anywhere throughout its range. Although widespread in its distribution, the pygmy killer whale is thought to be naturally rare. Despite the name, the pygmy killer whale is actually a dolphin and bears no physical resemblance to the killer whale.

Appearance:

The pygmy killer whale has a relatively small and slender body. It has a rounded head with no beak, and a tall falcate dorsal fin. The upper jaw contains 16 - 24 sharply pointed teeth, and the lower jaw 20 - 26, often with a distinctive white chin and lips. The flippers are long with rounded tips. Body colour is predominantly black or dark grey with a fairly distinct, yet narrow black dorsal cape. Some individuals may have white scratches and scars on the body. The snout and lips are more often than not white and there is also a white ventral band on the belly which widens towards the genital area. The pygmy killer whale may be confused with the false killer whale and the melon-headed whale, but the former has a more rounded head and flippers and a darker cape. It is also found in smaller groups, the dorsal cape is absent in false killer whales and scars are generally absent in melon-headed whales.

Behaviour:

Pygmy killer whales are usually found in groups of between 12 and 50 individuals, although groups of several hundred have also been recorded. These pods swim in coordinated lines which dissolve when they bunch together as they do if they become alarmed. They generally avoid boats, but will occasionally bow-ride and can be found logging at the surface in calm seas. Pygmy killer whales are usually slow swimmers, but may travel in bursts of speed and porpoise clear of the water. They rarely breach, but sometimes lobtail and spyhop. Throughout their range they seem to prefer deep warm waters and around some Hawaiian islands they have been found to display an extent of site-fidelity. Where studied, social bonds are known to be strong and stable. Although thought to feed mostly on a variety of species of fish and squid, they have been known to hunt other dolphins, especially those involved in fisheries interactions in the eastern tropical Pacific.

Distribution:

Pygmy killer whales are found in tropical and subtropical waters in all the world's oceans. They are rarely found near the coast except in areas where deep waters come close to the shore, for example in oceanic islands like Hawaii. This species is at risk from a substantial number of human-induced threats, which are compounded by the fact that it is thought to be a naturally uncommon species. Overfishing has led to severe population reductions of some prey species of the pygmy killer whale. It is taken in drive hunts in Japan, the Caribbean, Indonesia and Sri Lanka, and several hundred are killed annually as a result of bycatch in gillnets. They are vulnerable to loud anthropogenic noises, may be affected by climate change and have been known to ingest marine debris. The only existing population estimate for pygmy killer whales, approximately 39,000, is for the eastern tropical Pacific population. The IUCN lists this species as Least Concern.